Unique flow microscopic imaging and image processing capabilities embodied in commercially available IRIS instruments, The Yellow IRISR urinalysis workstation and The Purple IRISTM imaging cytometer, will be combined to form a prototype high speed, full color flow image processing system capable of differentiating leukocytes stained with Basic Orange 21 metachromatic dye supravital stain. The primary objective of this project is to demonstrate the effectiveness of a prototype automatic leukocyte differential counter utilizing this technology. Specifically, the capability of a prototype system to meet the analytical requirements of a Phase III commercial system and pass the NCCLS Leukocyte Differential Counting equivalence protocol, H20-T will be demonstrated and the design of a Phase III commercial system will be specified. This will provide validation and specification of a commercial instrument design based on proven available hardware. Thus, rapid funding and development of this instrument should be feasible. In addition, modification of the existing Yellow IRISR design would allow a leukocyte differential counting function to be added to this system thereby enhancing its utility.